The present invention relates to an optical coupler, more particularly relates to a waveguide type optical coupler for use as an optical modulator and an optical switch in an optical integrated circuit used in an optical fiber communication system, an optical information processing system, an optical sensing system, an optical data registration system and the like.
In the field of the optical communication system, in order to build up optical fiber communication networks, it is necessary to develop the optical device, such as an optical matrix switch, or the like. The optical directional coupler is a component of such a matrix switch.
Such an optical directional coupler is an element used to control in electro-optical effect a phase difference which dominates a transfer of electric power in case of approaching two parallel waveguides.